Persistent 'Effluence' Backdoor Exploited in Widespread Atlassian Confluence Attacks

A stealthy backdoor named Effluence has been discovered by cybersecurity researchers, persisting despite patching Atlassian Confluence servers. The backdoor allows for lateral movement to other network resources and data exfiltration from Confluence, and can be accessed remotely without authentication. The attack chain involves exploiting critical vulnerabilities in Atlassian Confluence, including CVE-2023-22515 and CVE-2023-22518, which allow for unauthorized administrator account creation and complete loss of confidentiality, integrity, and availability. The attacker gains initial access through CVE-2023-22515 and embeds a web shell that grants persistent remote access to every web page on the server. The web shell's loader component acts as a normal Confluence plugin, while the payload component executes malicious actions. The backdoor is potentially applicable to other Atlassian products as well.